Rotary piston machine with sealing elements

ABSTRACT

A rotary piston machine includes, arranged inside the gas-tight inner chamber (22) of a housing (24), a piston assembly (20) having at least three separate pistons (26) of identical design in the form of rectilinear prisms having front faces limited by several arcs of a circle (28, 30). The pistons are each fixedly secured to and turn in the same direction (36) as a shaft (34) rotatably mounted in the housing, extending through the geometric central axis and the rotation of which is synchronized by means of a gear, have flushed front faces and laterally limit the inner working space (38) with their curved circumferences, leaving a gap (S) between adjacent rotary pistons (26). Sealing elements (42) mounted in each gap (S) have two parallel sealing bars (44, 46) which have a cross section that is wider than the gap (S) are mutually linked by a connecting piece (48) narrower than the gap (S), and have a length that substantially corresponds to the length of the rotary pistons (26).

The invention relates to a rotary piston machine with sealing elements.In the case of the rotary piston machine with sealing elements of thiskind previously known from U.S. Pat. No. 3,809,026, the rotors areelliptical in cross-section and the sealing elements are constructed ofround sealing bars, which are mutually linked by the connecting piece.Due to this design, generally only one or two sealing bars of a sealingelement are in contact with the rotor's convex surfaces, the othersealing bar is free and protrudes without contact; this is illustratedin FIG. 8 of the patent text quoted. The sealing elements are thus notguided, and must be brought into the sealing position by auxiliarymeans, for example by the inner pressure.

This is where the invention steps in. It has as its objective theimprovement of the sealing system of a specific rotary piston machinewhich has an inner working space limited only by at least three rotarypistons.

On this basis the invention proposes for the solution of this objectivethat the front faces of the rotary pistons are limited by several arcs,which have two different radii R, r, of which the arc pieces with thesame radius R or r each have arc lengths equal to one another, which arealternately placed in contact at connection points and tangentiallyblend into one another at these points,

which are torsionally stiffly connected with the shafts respectivelyallocated to them, which shafts are rotatively mounted in the housing,extend along their geometric central axis, and are rotationallysynchronized with each other by means of a gear, with which they arerotatable in the same direction of turn,

which have front faces arranged flush with one another, and

which limit laterally an inner working space by means of their curvedperipheral surfaces,

whereby the radial spacing of the axis lines of the shafts is greaterthan the sum (R+r) of the two different radii R, r by the dimension of agap S between the adjacent rotary pistons, and the sealing bars eachhave the profile section of an isosceles, blunted triangle, whereby thecorners of the triangle point towards each other, the bases extendparallel to one other and the relationship ##EQU1## applies for theangle phi between the connecting line of the opposing blunted corners ofthe isosceles triangle and its sides, whereby K is the distance betweenthe respective parallel sides projected onto a line parallel to thebases, and K can be positive, negative or zero.

Such sealing elements are of simple design and are thus also simple tomanufacture; they are axially insertable into the gap between twoadjacent rotary pistons and in this way are easily mounted. Due to thisthey can also be easily replaced, by removing a front panel from thehousing.

The sealing elements are not fixedly secured to the rotary pistons,which they seal off from one another, rather, they are kept in place bythe fact that the one sealing bar is located on the one side of the gap,the other on the other side of the gap, both being identically designedsealing bars, however, having such large cross-section dimensions thatthey are unable to be moved through the gap. Due to the connecting piececonnecting them, they are also unable to move away from each other. Theyare therefore generally inserted or removed axially between two adjacentrotary pistons. In a preferred embodiment of the invention it isprovided that the connection piece be arranged to be detachable on atleast one side from the sealing bar located there. For this purpose, theone sealing bar can be connected with the connecting piece, for example,by means of a screw connection, by means of hooks, a clip connection orsuchlike. Such detachable sealing elements are favourable for specialmounting and dismantling purposes.

The gap between two adjacent rotary pistons is limited by the arcs withtheir differing radii, from which the rotary pistons are generated.Depending on the relative position of two adjacent rotary pistons to oneanother, the gap is limited by an arc with a large radius R on the oneside and an arc with a smaller radius r on the other side, with a mixedshape of both arcs in the area of the connection points, or with an arcwith a small radius r on the one side and an arc with the large radius Ron the other side. Thus, when operated in practice, the shape of the gapis constantly changing. Its gap width does indeed remain constant at alltimes at the narrowest point, but the distance of the curved surfaces ofthe adjacent rotary pistons changes at a specific distance from thisgap.

In other words, access to the gap becomes periodically narrower andwider, whereby, however, the actual gap width remains unchanged.

These changes in the gap must be taken into account in the design of thesealing elements. For this purpose the distance of the two sealing barstransversely to its longitudinal direction, which distance is determinedby the connecting piece, has been so selected that the sealing elementsalways have some play transversely to the gap and in all positions ofthe rotary pistons relative to one another. This means, however, thatthe sealing elements constantly move back and forth somewhat duringpractical operation. In doing so the following processes take place: ifthe inner working space enclosed by the rotary pistons is pressurized,the sealing bar of each sealing element located inside it will be pushedoutwards and brings about a seal. When the engine is rotating, massinertia forces are added to this, which bring about contact of the oneor other sealing bar of the sealing element, depending on whether thegap moves away from or approaches the centre point of the innercombustion chamber due to the rotation of the adjacent rotary piston.

Alternatively it is suggested each of the two sealing bars of thesealing elements be pulled up against one another by means of springs,by which means it is assured that the two sealing bars can indeed moveaway from one another and moved towards each other respectively,corresponding with the deformation of the gap, and yet both beconstantly in seal-tight contact.

By this means it is achieved simultaneously, where there is wear to thesealing bars and possibly to the peripheral surfaces of the rotarypistons, that, despite smaller dimensions, sealing contact is alwaysachieved in the event of wear.

Other advantages and features of the invention follow from the otherclaims as well as from the following description of practicalembodiments by way of examples which are not to be understood aslimiting, which examples of practical embodiments are explained in moredetail with reference to the drawing. In this

FIG. 1 shows a section through a rotary piston machine according to theinvention with inserted sealing elements,

FIG. 2 an illustration in perspective of a sealing element,

FIG. 3 an illustration corresponding with FIG. 2,

FIG. 4 an illustration in perspective of a sealing element with anelastic connecting piece,

FIG. 5 a front view of a rotary piston

FIG. 6 a section through two rotary pistons of a rotary piston machinewith a sealing element which is limited by straight lines.

FIG. 7 a side view of the sealing element of FIG. 6.

FIG. 8 an illustration of the gear arrangement for rotating the rotarypistons.

A piston arrangement 20 is shown in FIG. 1 in section of a rotary pistonmachine, which is located inside a gas-tight inner space 22 of a housing24. It is formed by three rotary pistons 26 with identical design to oneanother, which rotary pistons are designed as rectilinear prisms. Theircross-section surfaces can be seen in FIG. 1, the front faces areidentical. The front faces are limited by a total of six arc pieces 28,30 (or four arc pieces 28, 30 in FIG. 5), which have different radii,namely one larger radius R and a smaller radius r. The circular arcpieces with the same radius, R, or r, each have the same base length asone another. The arc pieces 28, 30 are placed in contact with oneanother alternately at connection points, at these they tangentiallyblend into each other.

Each rotary piston 26 is allocated with a shaft rotatively mounted inthe housing 24, connected to its torsionally stiffly, which extendsalong its geometric central axis. The separate shafts are rotationallysynchronized with each other by means of a gear 101 (see FIG. 8), sothat the relative angular position of the separate rotary pistons 26 isretained relative to one another. The rotary pistons 26 are rotatable inthe same direction of turn in the direction of an arrow 36. The frontfaces of the rotary pistons 26 are arranged flush with one another, andare hence located at the respectively same levels.

The three rotary pistons 26 limit laterally by means of their curvedperipheral surfaces an inner working space 38 which is limited at itsend regions by surfaces of the housing 24.

The radial distance of the axis lines 40 of the shafts 34 of adjacentrotary piston 26 is greater than the sum of the two different radii bythe dimension of a gap S, thus R+r. Due to this, said gap S remains freebetween adjacent rotary pistons 26. Its gap width S' at the narrowestpoint is constant by virtue of the shape of the rotary pistons 26 andtheir geometric arrangement on the shafts 34.

The seal tightness between adjacent rotary pistons 26 is achieved bysealing elements 42; in total equally as many sealing elements 42 areprovided as gaps S between the rotary pistons 26. The sealing elementsare composed of two sealing bars 44, 46, which are parallel to oneother, and a connecting piece 48 linking these. The sealing bars 44, 46are preferably designed identically and have the length of the rotarypistons 26. They have a cross-section width Q which is greater than thewidth of the gap S, due to which it is prevented that it is able to slipthrough the gap S. The two sealing bars 44, 46 of a sealing element arelocated on both sides of the gap S. The connecting piece 48 transversethe gap itself, which piece is narrower than the width of the gap S.

In the practical embodiment by way of the example according to FIGS. 1and 2, the sealing bars 44, 46 have a profile of a truncated triangle,the connecting piece is formed by a narrow stay, which has recesses 50for the purpose of saving weight. In a practical embodiment by way ofexample the large radius R is equal to 60 millimeters, the small radiusr is equal to 15 millimeters.

In the practical embodiment by way of the example according to FIG. 3both sealing bars 44, 46 are tubes which are utilized simultaneously forthe supply of a lubricant. The connecting pieces 48 are transverselyextending tubes, which have aperatures for the egress of lubricant.Overall this sealing element 42 has the form of a ladder with sparshaving the profile of a truncated triangle and round rungs.

The aperatures for supplying lubricant are also shown in FIG. 6 as holes102 running length wise through sealing elements 44, 46 and in FIG. 7 asaperatures 103 in connecting piece 48.

The practical embodiment by way of example in accordance with FIG. 4, asealing element 42 is finally shown, in which the two sealing bars 44,46 have a cross-section of a truncated triangle. The trunicated pointsof the parabolas point towards each other. The connecting piece 48 isonce again arranged in the form of round rungs, these are connected attheir one end rigidly with the lower sealing bar 44, however, protrudewith their other end region through openings in the upper sealing bar46. The terminate at the top in discs 52. Spiral compression springs 54are arranged between these and the flat surface of the upper sealing bar46, which springs press the two sealing bars 44, 46 up against eachother. By this means it is brought about, as described above, that thetwo sealing bars 44, 46 are each in contact with the convex surfaces ofthe rotary pistons 26 and no play occurs as exists by necessity in theembodiment by way of example in accordance with FIGS. 2 and 3.

The rotary pistons 26 in the practical embodiment by way of example inaccordance with FIG. 1 have a 120 degree rotational symmetry. Rotarypistons 26 with other rotational symmetries can also be used, forexample with 180 degree rotational symmetry; on this subject referenceis made to FIG. 5 and simultaneously to the application of the same dateand by the same applicant "stirling machine . . . ", whose contentbelongs to the full scope of the disclosure of the present application,DE-A- NO. 3644833.8 Dec. 31, 1986.

The design of the front faces or cross-section surfaces of the rotarypistons 26 can be seen in FIG. 5 in the case of a 180 degree rotationalsymmetry. The rotary pistons' cross-sections shown there are essentiallyelliptical. The ellipse has two main semi-axes and two main secondarayaxes, which in each case extend from the centre point, this being theintersection point of axis line 40 of the pertinent shaft 34 with thelevel of the paper. The two main semi-axes are positioned at 180 degreesto one another. In the illustration they extend from top to bottom. Thetwo secondary semi-axes are also at an angle of 180 degrees to oneanother, they extend from left to right and at an angle of 90 degrees tothe main semi-axes.

For the purpose of designing, a circle with a radius of r_(T) is drawnabout the axis line 40, which circle intersects the two main andsecondary axis lines, which are at 90 degrees to one another, at a totalof four points 56 to 62. An arc with the large radius R is drawn aboutthe intersection points 56, 58 with the secondary axis lines. Circleswith the small radius r are drawn about the two points 60, 62, thesebeing the intersection points of the circle with radius r_(T) with thetwo main axis lines. The radii are inter-related in terms of thefollowing formula:

    R-r=2r.sub.T x cos 90°/n.

In the practical embodiment by way of example in accordance with FIG. 1,n is equal to three, in the practical embodiment by way of example inaccordance with FIG. 5, n is equal to two.

In the practical embodiment by way of example in accordance with FIG. 6the sealing bars 44, 46 of the sealing element 42 each have the profilesection of an isosceles triangle or a blunted triangle. The corners ofthe two triangles point towards each other, the bases 64 extend parallelto one another and at right-angles to a an interconnecting line 65 ofthe points located opposite to them. The two triangles are congruent.The projected distance of each of the parallel sides 66, 67 isdesignated by K on a line parallel to the bases 64. Phi is the anglebetween the interconnecting line 65 and the sides 66, 67. ##EQU2##applies.

K may be positive, negative or zero; the positive case is shown in FIG.6. The advantage of the arrangement in accordance with FIG. 6 lies inits exact fit. The connecting piece 48 can be executed optionally, e.g.as in the previously discussed practical embodiments by way of example.

I claim:
 1. Rotary piston machineA. with a piston assembly arranged in agas-tight inner chamber of a housing, which arrangement is composed ofat least three separate rotary pistonswhich are of identical design toone another, which are in the form of rectilinear prisms whose frontfaces are limited by arcs, whereby the radial spacing of the axis linesof the shafts is greater than the corresponding dimensions of the rotarypistons by the dimension of a gap S between adjacent rotary pistons,whereby a sealing element is allocated to each gap, which elements eachhave two sealing bars parallel to one another,which have a cross-sectionwhich is wider than the width S' of the gap S, which are in each casecongruent, which are mutually linked by a connecting piece which isnarrower than the width S' of the gap S and which have a length whichcorresponds substantially with the length of the rotary pistons, whereinthe front faces of the rotary pistons are limited by several arcs whichhave two different radii, R, r of which the arc pieces with the sameradius R or r each have arc lengths equal to one another, which arealternately placed in contact at connection points and tangentiallyblend into one another at these points, which are torsionally stifflyconnected with the shafts respectively allocated to them, which shaftsare rotatively mounted in the housing, extending along their geometriccentral axis, and are rotationally synchronized with each other by meansof a gear, with which they are rotatable in the same direction of turn,which have front faces arranged flush with one another, and which limitlaterally an inner working space by means of their curved peripheralsurfaces, whereby the radial spacing of the axis lines of the shafts isgreater than the sum (R+r) of the two different radii R, r by thedimension of a gap S between the adjacent rotary pistons, and thesealing bars each have the profile section of an isosceles, bluntedtriangle, whereby the corners of the triangle point towards each other,the bases extend parallel to one another and the relationship ##EQU3##applies for the angle phi between the connecting line of the opposingblunted corners of the isoceles triangle and its sides, whereby K is thedistance between the respective parallel sides projected onto a lineparallel to the bases, and K can be positive, negative or zero. 2.Rotary pistons machines according to claim 1, wherein the connectingpiece is elastic.
 3. Rotary piston machines according to claim 1,wherein the width of the connecting piece is five percent to fiftypercent smaller than the width of the gap S.
 4. Rotary piston machineaccording to claim 1, wherein the sealing bars have an oil boring forthe supply of lubrication oil to the sealed zone between the rotarypistons.
 5. Rotary piston machine according to claim 1, wherein equallyas many sealing elements are provided as are rotary pistons.
 6. Rotarypiston machine according to claim 1, wherein the rotary pistons have a180 degree to 120 degree rotational symmetry.
 7. Rotary piston machineaccording to claim 1, wherein the sealing bars are pressed onto therotary pistons by means of compression springs.
 8. Rotary piston machineaccording to claim 1, wherein the sealing bars have flat seal surfacesin longitudinal direction, and with these are in contact with the rotarypistons.
 9. Rotary piston machine according to claim 1, wherein theradii R and r of the arcs are related to one another in accordance withthe formual ##EQU4## whereby the center points of the arcs lie on mainand secondary axis lines of the rotary piston cross-section, beingsimilar to an ellipse, and being at a distance of r_(T) from the axisline, whereby n is an integer.